Lesson · Grade 7 · Mathematics
Multiplying and Dividing by 10, 100 and 1000
- Grade 7
- Mathematics
- 1 min 18 s
- British Columbia
- BC7-MA-20
On a place value chart with the decimal point held still, 4.7 × 100 is worked out by moving each digit two places left, one for each zero in 100, because every place to the left is worth 10 times more, and a placeholder zero fills the ones place to give 470. Dividing 470 by 100 moves the digits two places back to the right to give 4.70, which is 4.7, and the video ends on the rule of one place per zero, left to multiply and right to divide, for 10, 100 and 1000.
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In one sentence
The question this lesson answers
What is 4.7 times 100?
First, write 4.7 on a place value chart.
Transcript
What the lesson says
What is 4.7 times 100?
First, write 4.7 on a place value chart.
The decimal point stays still, and the digits move around it.
Each place is worth 10 times the place to its right.
100 has two zeros, so each digit moves two places.
Multiplying makes the number bigger, so the digits move to the left.
The ones place is now empty, so we fill it with a zero.
So 4.7 times 100 is 470.
Now let us undo it and divide 470 by 100.
Dividing makes the number smaller, so the digits move two places to the right.
4.70 is the same as 4.7, so we can drop the last zero.
So 470 divided by 100 is 4.7, right back where we started.
It works the same way for 10 and 1000: one place for each zero.
To recap, the digits move one place per zero: left to multiply, right to divide.
Curriculum
Where this fits
- British Columbia, Grade 7
Mathematics, Number: operations with decimalsBC7-MA-20
Previous: Dividing a Decimal by a Whole NumberNext: Order of Operations with Decimals and Brackets
The outcomes and strands follow the British Columbia curriculum.
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